Studies with animal-tumor models have shown that tumor growth is enhanced by nutritional regimens that replenish the malnourished host. However, clinical observations based upon x-rays and physical examination have not detected changes in tumor growth. These methods for detecting tumor growth are insensitive to subtle changes in tumor growth on the molecular level. The purpose of this proposal is to evaluate the effects of preoperative intravenous hyperalimentation (IVH) on tumor growth parameters as measured by cell kinetic analysis. Patients who have a biopsy proven rectal cancer and who require at least seven days of preoperative IVH will be eligible for this study. Rectal cancer has been selected for this study because adequate tissue sampling of the tumor can be easily obtained through a proctoscope. Rectal tumor biopsies will be obtained before IVH is started, during IVH and at the completion of preoperative IVH just before the surgical resection is done. All tumor sampling will be accomplished by the proctoscope to insure uniform conditions for tissue sampling. Tumor tissue and adjacent normal rectal mucosa will be analyzed for growth fraction, percent cells in S-phase and DNA, RNA and protein content as measured by flow cytometry. The initial tumor cell kinetic parameters will be compared with the subsequent kinetics parameters for each tumor.